Why does my gun's bullet collide with the muzzle?

So i made a gun. And it works fine. But if i aim, and shoot, it collides with the muzzle, so the bullet doesnt go anywhere. If i dont aim, it works fine. Why is that?

function script:

function shoot()
    if not reloading then
        if ammo.Value > 0 then
            if not changingmodes then
                if not idk then
                  if not runnin then
                aui.Frame.bullets.Text = ammo.Value.."/"..clips.Value
                        local sound = selectedgun.Sound
    local ss = sound:Clone()
    ss.Playing = true
    ss.Parent = cam

    game:GetService("Debris"):AddItem(ss,2)
    local ray = Ray.new(selectedgun.Thingy.CFrame.p, (m.Hit.p - selectedgun.Thingy.CFrame.p).unit * 300)
    local part, position = workspace:FindPartOnRay(ray, p.Character, false, true)
    local b = Instance.new("Part")
    b.CanCollide = false
    b.Anchored = true
    b.Transparency = 0
    b.Size = Vector3.new(1.25, 0.25, 0.25)
    re = re * gunds.shooten
    local distance = (selectedgun.Thingy.CFrame.p - position).magnitude
        b.Size = Vector3.new(1, 1, 1)
        b.CFrame = CFrame.new(selectedgun.Thingy.CFrame.p, position) * CFrame.new(0, 0, -distance / 2)
        game:GetService("Debris"):AddItem(b, 0.1)
        local bh = misc.bullethole:Clone()
        bh.Parent = workspace
        bh.CFrame = CFrame.new(position)
        game:GetService("Debris"):AddItem(bh,3)
        if part then
    local humanoid = part.Parent:FindFirstChild("Humanoid")

    if not humanoid then
        humanoid = part.Parent.Parent:FindFirstChild("Humanoid")
    end

    if humanoid then       
        if part.Name == "Head" then
                    humanoid:TakeDamage(50*2)

                    print("hEaDsHoT")
        else
                    humanoid:TakeDamage(30)
        end
    end
        end
                    ammo.Value = ammo.Value - 1
            end
            end
    else
    end
    aui.Frame.bullets.Text = ammo.Value.."/"..clips.Value
    if settings.something.Value == 1 then
    aui.Frame.mode.Text = "Automatic"
end

            end
            end

end

thanks for helping!